Concentration of phosphate-bearing material



Patented June 20, 1933 UNITED STATES PATENT OFFICE LAwRENcE n. LANGE, or SALT LAKE cm, UTAH, ASSIGNOR TO THE GENERAL ENGINEERING COMPANY, on SALT LAKE CITY, UTAH, AconPoRAnoN OF UTAH CONCENTRATION OF PHOSPHATE-BEARING MATERIAL No Drawing.

This invention relates to the concentration of phosphate-bearing material and has for object certain improvements in the method of concentrating phosphate-bearing material by froth flotation. The invention relates more particularly to the froth flotation of phosphatic material associated with quartz gangue constituents.

In the heretofore customary method of concentrating phosphate-bearing material by froth flotation, the phosphate-bearing particles are floated While the gangue constituents are depressed. The concentration of phosphate-bearing material in this manner is rendered somewhat difficult because the phosphate-bearing particles tend to partake of the nature of the gangue constituents. Although a substantial portion of the phosphate-bearing particles may be thus concentrated, there is a tendency for gangue constituents to nocompany the hosphate particles into the froth layer mamtaine'd on the surface of the body of pulp undergoing the froth flotation operation, as well as for phosphate-bearing particles to be depressed together with gangue constituents that go into the tailings.

As a result of my investigations, I have determined that phosphate-bearing material may be subjected to a froth flotation operation in which the gangue constituent-s are floated and the phosphate-bearing particles are depressed. Flotation reagents may be employed that alone or in combination with one another selectively float the gangue constituents and selectively depress the phosphate-bearing particles. This up-sidedown step 1s particularly effective in separating quartz constituents from phosphatebearing particles.

According to the present invention, a phosphate-bearing material is subjected in the form of a pulp to a froth flotation operation .in the presence of flotation reagent adapted selectively to float gangue constituents and to depress phosphate-bearing particles.

While the flotation process of the invention may be conducted with phosphate-bearing material containing slimes, a better separation of the phosphate-bearing particles from the gangue constituents is obtained when the Application filed February 4, 1931. Serial No. 513,354.

slimes are first substantially removed. The presence of slimes in the pulp is furthermore objectionable because the consumption of flotation reagents tends to increase.

In order to obtain a sharp separation of phosphate-bearing particles from gangue constituents, -the material should be in a fine state of subdivision. As far as my investigations thus far have gone, best results appear to be obtained when the flotation operation is conducted on material ranging in size from approximately 28 to 200 mesh.

Phosphate-bearing material of the fine state of subdivision contemplated necessarily includes a substantial amount of minute particles falling within the so-called slime range.

It is therefore better practice first to subject I tion reagents adaped to float the gangue constituents. Thus, any suitable frothing agent of commerce may be employed; such as pine 01], coal tar derivatives, wood-oils, or any appropriate hydrocarbon and the like.

The de-slimed phosphate-bearing pulp is then suitably treated in order to effect the froth flotation of gangue constituents and to depress phosphate-bearing particles. In order to inhibit the flotation of the phosphate-bearing particles, while leaving the gangue constituents in a condition amenable to flotation, flotation reagents functioning in a peculiar and novel manner must be employed.

Gangue constituents such as quartz are not readily floated in an acid circuit. It is therefore necessary to render the mineral pulp properly alkaline. Lime (CaO) is highly useful for this purpose. In fact, it serves a triple function. While assisting in rendering the pulp highly alkaline, it also acts as a depressant to the phosphate-bearing particles; and as a collector for the gangue particles, when used in conjunction with another appropriate reagent, such as sodium oleate.

to produce alkalinity; but their use appears to necessitate the employment of more de- Y starches.

pressant reagents than is needed when they are employed in conjunction wlth lime. These other alkaline reagents do not,moreover, appear to yield as marked a differential separation as with the use of lime.

In order to make the-gangue constituents, such as quartz, floatable, suitable flotation reagents must be employed. Thus, compounds producing the oleate radical and metallic salts, such as lead nitrate, in solution, are highly effective; For example, a metallic soap such oil soap, acid mass sodium oleate, or ordinary soap are suitable. A soap compound called olate on the market is particular] eflicacious in the operation contemplate Metallic salts such as ferrous sulphate, copper sulphate, zinc sulphate, aluminumsulphate, lead nitrate, copper nitrate, ferrous nitrate, and ferric nitrate or the like may be emloyed to assist in the flotation step. Alcoiiohc solutions (denatured alcohol or methanol) of the different soaps and oleic acid are highly effective in causing quartz to float.

As stated above, the presence of lime in the pulp body not only assists in making the circuit alkaline; but it also tends to exert a depressant action on the phosphate-bearing particles. This depressant action is materially aided by the addition of a proper amount of a suitable carbohydrate, such as the well known Starch and lime in the mineral pulp not only tend to sink. the phosphatebearing particles, but they also assist in modifying the gangue constituents so as to make them amen able to the floating step.

Although the soaps produce considerable forth, the froth does not generally have sufficient stability to support its burden of gangue constituents. Additional frothing agent or agents should therefore be employed in conjunction with those particularly intended to depress the phosphate-bearing particles and to float the gangue constituents. Practically any of the conventional frothing agents maybe employed, such as pine oil, coal tar derivatives, wood oils and the like. A coal tar derivative called tarol has been found to give unusually good results.

The flotation operation may be conducted in any suitable froth flotation apparatus. Thus, the well known Callow or MacIntosh cells may be employed. Finely disseminated air under pressure is released into the body of pulp at or near its bottom. As the air bubbles rise they tend selectively to be attached to the gangue constituents and lift them to the froth layer maintained on the surface.

The procedure for agitation of the pulp and flotation may be varied in certain respects. Thus, when employing lime an starch, agitation should precede the flotation as sodium oleate in the form of red step. If tarol is used, it should be added during the agitation'period in order to cause dispersion of the reagent throughout the pulp body. If, on the other hand, pine oils are used, they may be added either before or after agitation of the pulp body. The point at which the frothing agent is added depends largely on its property of dispersion in aqueous solutions.

The metallic salts, such, for example, as copper sulphate, may be added either before or after agitation; but when added before agitation, the soap consumption is decreased. The soaps have no marked effect when added to the pulp during the agitation period. Hence, it is preferable to add the soap to the pulp in the flotation cell, where its desired action may at once be obtained.

If tarol is. employed as-a frothing agent, sodium oleate is the only reagent that needs to be added to the alkaline flotation circuit.

Excellent results are obtained when employin this combination. efliciency and consequently to decrease excess consumption, it is advantageous to add the soap at intervals throughout the duration of the flotation step.

lVhen employing lime and tarol, they are preferably added to the mineral pulp during the agitation period, i. e., prior to the actual flotation of the quartz constituents. As a re- To obtain the greatest sult of the agitation of the pulp in the presence of the lime and tarol, the slimes are substantially floated away. The olate is thenadded, and the quartz particles are removed by froth flotation.

Extensive deposits of so-called phosphate rock are found in Florida. bearing material contains substantial amounts of quartz, sometimes referred to as silica sand. Thematerial is found in nature for the most part in a finely subdivided state, many of the smallest particles falling within the so-called slime range. The phosphate is present generally as tricalcium phosphate. My invention as practiced on this material has shown very excellent results. To illustrate the practice of the present invention, the data submitted below may be considered in the examples set out. The amounts of reagents specified are, as is conventional, computed on the basis of per ton of feed treated.

Example No. 1

This phosphate- Percent B. P. L. bone phosphate of lime) in concentrates=15.2%.

Percent B. P. L. (bone phosphate of hme) in tailings=66.0%. I

Recovery of B. P. L. in ta1l1ngs=77.%.

Ewample No. 2

In a test run on minus 48 to plus 200 meshfeed, the following procedure was employed,

producing a good grade of quartz concentrate with very small amounts present In the tailing :An average portion of the ore was a tated for a period of five minutes at 1 to-1 pu p density with 25' pounds lime, 2 pounds starch, 1 pound copper sulphate, and 2 pounds tarol. After agitation, the slimes produced therefrom were floated 03, followed by the addition of 1.35 pounds of sodium oleate (red oil soap). Flotation was carried on at'a pulp density of 3 to 1.

Percent B. P. L. in concentrates=15.2%. Percent B. P. L. in tailings =71.83%. Recovery of B. P. L. in taihngs=70.%.

E's-ample 1V 0. 3

In another test, an average portion of the order to reduce the size of the coarser parti cles of quartz to make them more amendable to flotation. The ground product was then roughly de-slimed, and the de-slimed product was, added to the minus 48 mesh feed from the screening. This product was then given a. 10

40 minute agitation (1 to 1 pulp density) with 25 pounds lime (CaO) per ton of ore and 3 pounds of tarol per ton of ore. After agitation, the slimes produced therefrom were floated off, followed by the addition of 1.0

pound oleate soap compound. The flotation operation was then carried out at a pulp density of 3 to 1.

- Percent Percent B. P. L. in slimes from grinding 63.9 Percent B. P. L. in concentrates 12.4 Percent B. P. L. in tailings 73.9 Recovery of B. P. L. in slimes 7.3 Recovery of B. P. L. in tailings 65.4 Total recovery of B. P. L. 72.7

vance of the flotation step itself. The conditioning period, for example 30 minutes,

' with the lime appears to cause a wetting of the phosphate-bearing particles, and thus renders them non-amendable to froth flotation when the collecting agent, such as soap, is ultimately added. The frothing agent, such as steam distilled pine oil, is advantageously present in the pulp during the conditioning period, thuspermitting a thorough dissemination of the pine oil 'rior'to the introduction of the pulp to the otation cell.

I claim: ,1. In a method of concentrating phosphate-bearing' material in a fine state of subdivision by froth flotation, the step which comprises subjecting the phosphate-bearing material in the form of an alkaline pulp to a'conditioning period until the phosphatebearing particles are rendered non-amendable to froth flotation when the collecting agent is added to the pulp whereby gangue constituents may be selectively floated while the phosphate-bearing particles are depressed. I

2. Process according to claim 1, in which lime is added to obtain the desired alkalinity, said lime being adapted also to act as a depressant to the phosphate-bearing particles.

3. Process according to claim 1, in which a carbohydrate is added, said carbohydrate being adapted to act as. a. depressant to the phosphate-bearing particles.

4. Process according to claim 1, in which a starch is added, said starch being adapted to act as a depressant to the phosphate-bearing particles.

5. Process according to claim 1, in which lime and starch are added to obtain the desired alkalinity and to depress the phosphatebearing particles.

6. Process according to claim 1, in which lime, starch and an oil are added to obtain the desired alkalinity and to depress the phos phate-bearing particles.

7. Process according to claim 1, in which starch and soap are added.

8. Process according to claim 1, in which starch and a metallic soap areadded.

9. Process according to claim 1, in which starch an sodium oleate are added.

10. Process according to claim 1, in which starch and potassium oleate are added.

11. Process according to claim 1, in which starch and red oil soap are added.

12. Process according to claim 1, in which starch and acid mass sodium oleate are added.

13. Process according to claim 1, in which starch and an alcoholic soap solution are added.

14. Process according to claim 1, in' which starch and oleic acid are added.

15. Process according to claim 1, in which starch and soap and a metalli'c'salt in solution are added.

16. Process according to claim 1, in which starch and soap and a metallic sulfate in solution are added.

17. in ileoholip solution Process acoordini to claim 1, in which 0 soap and oleic acid are added.

Process according to claim 1, in which and a metallic salt in solution are added. testimony whereof I gflix my signature LAWRENCE H. LANGE. 

